While Demi Lovatois getting closer with on-again, off-again boyfriend Wilmer Valderrama off screen, she's starting a new romance on screen. For her upcoming guest role on the fifth season of Glee, Lovato will playing the lesbian love interest toNaya Rivera's character Santana Lopez.

"She's playing my love interest, so I'm very, very excited about that," Rivera, 26, told MTV News on Sunday, Aug. 25 about the 21-year-old singer joining the Fox musical series. "We get to sing a song together. It's gonna be good. I'm excited to work with her. We're bringing her to the dark side. Well, she comes in in a Beatles episode, so [we're singing] a Beatles song. I'm excited." (Rivera's character has previously been in a romantic relationship with Heather Morris' Brittany Pierce on the show.)

Lovato also tweeted her excitement about joining Glee on Monday, Aug. 26, writing, "Wayyyyy too excited to be starting @GLEE this week!!!!!!! Asjfkdjshdk. I can't believe I'm going back to acting but the best part about it is that I get to act/sing with some of my really great friends . . ."

Getting back to work on a new season of Glee is bittersweet for Rivera. CostarCory Monteith died from a heroin and alcohol overdose on July 13. While mourning his death, the cast has been working on filming a special tribute episode, airing October 10. At the 2013 MTV Video Music Awards on Sunday, Rivera told Us Weekly the mood on set has been "terrible."

The actress also told MTV News, "It's horrible. So many, so many [memories]. He was an amazing guy and I definitely miss him."